New observations from the James Webb Space Telescope (JWST) reveal that exoplanet WASP-107b is rapidly shedding its atmosphere, with a massive plume of helium gas trailing behind it as it orbits its star. This discovery provides unprecedented insight into how gas giants behave in extreme stellar environments and why some planets end up so different from those in our own solar system.
The “Super-Puff” Phenomenon
WASP-107b, located roughly 210 light-years from Earth, is classified as a “super-puff” exoplanet due to its unusually low density. At 94% the size of Jupiter, it contains only 12% of the gas giant’s mass — making it remarkably inflated for its weight. This makes WASP-107b a rare case among exoplanets.
The JWST observations, published in Nature Astronomy, detected a helium gas cloud extending nearly five times the planet’s diameter. This plume isn’t static; it’s actively escaping the planet, moving ahead of WASP-107b in its orbit. This is the first time such atmospheric escape has been directly observed with JWST, giving scientists a clear view of the process.
Planetary Migration and Atmospheric Loss
The extreme conditions around WASP-107b are key to understanding its fate. The planet orbits seven times closer to its star than Mercury does to the sun, subjecting it to intense heat that is stripping away its outer layers. But WASP-107b didn’t always live so close: scientists believe it migrated inward from a more distant orbit, possibly pushed by gravitational interactions with another planet in the system (WASP-107c).
“WASP-107c could have played a role in this migration,” says study co-author Caroline Piaulet-Ghorayeb. This suggests that planetary reshuffling is a common process in star systems, leading to unexpected arrangements.
Once close to its star, the heat began eroding WASP-107b’s atmosphere. The JWST observations confirmed this: the helium cloud was detected 1.5 hours before the planet itself passed in front of its star. This means the atmosphere is actively being blown away in real time.
Atmospheric Composition Reveals Clues
Beyond helium, the JWST also detected water, carbon monoxide, carbon dioxide, and ammonia in WASP-107b’s atmosphere – confirming previous Hubble Space Telescope observations. Surprisingly, the expected methane was absent. This suggests that the atmosphere is undergoing “vigorous vertical mixing,” with heavier gases from deeper layers being pulled upward due to the star’s heat.
The presence of more oxygen than expected also supports the theory that WASP-107b is a recent migrant, as its current conditions wouldn’t allow for such high oxygen levels if it had formed closer to its star.
In conclusion, the JWST’s observations of WASP-107b provide a unique snapshot of atmospheric loss in action. The discovery highlights the dynamic processes shaping exoplanet atmospheres and underscores the importance of planetary migration in creating the diverse worlds beyond our solar system.
